Development of Mesoporous Silica Nanoparticle-Based Films with Tunable Arginine-Glycine-Aspartate Peptide Global Density and Clustering Levels to Study Stem Cell Adhesion and Differentiation.

Stem cell adhesion is mediated via the binding of integrin receptors to adhesion motifs present in the extracellular matrix (ECM). The spatial organization of adhesion ligands plays an important role in stem cell integrin-mediated adhesion. In this study, we developed a series of biointerfaces using arginine-glycine-aspartate (RGD)-functionalized mesoporous silica nanoparticles (MSN-RGD) to study the effect of RGD adhesion ligand global density (ligand coverage over the surface), spacing, and RGD clustering levels on stem cell adhesion and differentiation. To prepare the biointerface, MSNs were chemically functionalized with RGD peptides via an antifouling poly(ethylene glycol) (PEG) linker. The RGD surface functionalization ratio could be controlled to create MSNs with high and low RGD ligand clustering levels. MSN films with varying RGD global densities could be created by blending different ratios of MSN-RGD and non-RGD-functionalized MSNs together. A computational simulation study was performed to analyze nanoparticle distribution and RGD spacing on the resulting surfaces to determine experimental conditions. Enhanced cell adhesion and spreading were observed when RGD global density increased from 1.06 to 5.32 nmol cm-2 using highly clustered RGD-MSN-based films. Higher RGD ligand clustering levels led to larger cell spreading and increased formation of focal adhesions. Moreover, a higher RGD ligand clustering level promoted the expression of alkaline phosphatase in hMSCs. Overall, these findings indicate that both RGD global density and clustering levels are crucial variables in regulating stem cell behaviors. This study provides important information about ligand-integrin interactions, which could be implemented into biomaterial design to achieve optimal performance of adhesive functional peptides.

Anti-metastatic effect of ranolazine in an in vivo rat model of prostate cancer, and expression of voltage-gated sodium channel protein in human prostate.

BACKGROUND: Voltage-gated Na+ channels (VGSCs) are functionally upregulated in rat and human prostate cancer (PCa) where channel activity promotes cellular invasiveness in vitro and metastasis in vivo. Ranolazine is a clinically used VGSC inhibitor/anti-anginal drug, which has been shown previously to inhibit breast cancer metastasis in vivo. METHODS: Using the Dunning model of rat PCa, the effect of ranolazine applied systemically (by gavage) was tested on the development of primary tumours and metastases following subcutaneous inoculation of Mat-LyLu cells into Copenhagen rats. In addition, human prostate tissue microarrays were used to determine VGSC protein expression in cancerous versus non-cancerous tissue. Several public databases were searched to compare Nav1.7/ SCN9A expression levels in 'normal' vs. PCa tissues. RESULTS: Ranolazine (2.5 and 5 µM) decreased the number of lung metastases by up to 63%. In contrast, primary tumourigenesis was not affected. Ranolazine also reduced the percentage of cells in the metastases expressing Nav1.7, the main VGSC subtype expressed in PCa, but the expression level was higher. In prostate tissue microarrays, VGSC protein expression was significantly higher in cancerous versus non-cancerous tissue. There was no correlation between the VGSC expression and either prostate-specific antigen or Gleason score. In public databases, little information could be found on Nav1.7 protein expression in PCa. In addition, the database information on Nav1.7 mRNA (SCN9A) expression levels did not correlate with previously reported upregulation in PCa cells and tissues. CONCLUSIONS: The main conclusions were (i) ranolazine inhibited metastasis and (ii) it was a subpopulation of cells with particularly high levels of Nav1.7 protein that reached the metastatic sites. These data extend earlier studies and suggest that Nav1.7 expression could serve as a functional biomarker of metastatic PCa and that VGSC blockers may be useful as anti-metastatic agents.

Gabapentin, an Analgesic Used Against Cancer-Associated Neuropathic Pain: Effects on Prostate Cancer Progression in an In Vivo Rat Model.

A major problem associated with clinical management of cancer is controlling the accompanying pain, and various analgesics are in common use for this purpose. Recent evidence suggests that some of the targets of analgesics, such as ion channels and receptors, may also be involved in the cancer process, thereby raising the possibility that such use of some analgesics may impact upon cancer itself. The main aim of this study was to determine whether gabapentin, a common adjuvant analgesic in current use against cancer-associated neuropathic pain, would affect tumour development and progression in vivo. The Dunning rat model of prostate cancer was used. Strongly metastatic Mat-LyLu cells were implanted subcutaneously into syngeneic Copenhagen rats which were then treated every other day with 4.6-16.8 µg/kg gabapentin by gavage. Primary tumourigenesis was monitored daily. Lung metastases were counted and measured after killing the rats 21 days later. Gabapentin had no effect on primary tumourigenesis but produced dose-dependent effects on lung metastasis. Whilst 4.6 µg/kg had no effect, 9.1 µg/kg gabapentin decreased the number of lung metastases significantly by 64%. In contrast, 16.8 µg/kg gabapentin promoted metastasis significantly by 112% and showed a strong tendency to shorten mean survival time. It is concluded that gabapentin prescribed to cancer patients against pain could impact upon the cancer process itself.